proxmox-mirrors/wasi-libc
1
0
Fork 0
mirror of https://git.proxmox.com/git/wasi-libc synced 2025-08-09 03:26:32 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Fix races around pthread exit and join (#409)

Browse Source
This commit is contained in:
YAMAMOTO Takashi 2023-06-08 01:51:07 +09:00 committed by GitHub
parent a6f8713433
commit aecd368c6d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 26 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Makefile
View File

@ -325,6 +325,7 @@ ifeq ($(THREAD_MODEL), posix)
# Specify the tls-model until LLVM 15 is released (which should contain # Specify the tls-model until LLVM 15 is released (which should contain
# https://reviews.llvm.org/D130053). # https://reviews.llvm.org/D130053).
CFLAGS += -mthread-model posix -pthread -ftls-model=local-exec CFLAGS += -mthread-model posix -pthread -ftls-model=local-exec
ASMFLAGS += -matomics
# Include cloudlib's directory to access the structure definition of clockid_t # Include cloudlib's directory to access the structure definition of clockid_t
CFLAGS += -I$(LIBC_BOTTOM_HALF_CLOUDLIBC_SRC) CFLAGS += -I$(LIBC_BOTTOM_HALF_CLOUDLIBC_SRC)

22
libc-top-half/musl/src/thread/pthread_create.c
View File

@ -164,14 +164,6 @@ static void __pthread_exit(void *result)
self->prev->next = self->next; self->prev->next = self->next;
self->prev = self->next = self; self->prev = self->next = self;
#ifndef __wasilibc_unmodified_upstream
/* On Linux, the thread is created with CLONE_CHILD_CLEARTID,
* and this lock will unlock by kernel when this thread terminates.
* So we should unlock it here in WebAssembly.
* See also set_tid_address(2) */
__tl_unlock();
#endif
#ifdef __wasilibc_unmodified_upstream #ifdef __wasilibc_unmodified_upstream
if (state==DT_DETACHED && self->map_base) { if (state==DT_DETACHED && self->map_base) {
/* Detached threads must block even implementation-internal /* Detached threads must block even implementation-internal
@ -190,9 +182,6 @@ static void __pthread_exit(void *result)
} }
#else #else
if (state==DT_DETACHED && self->map_base) { if (state==DT_DETACHED && self->map_base) {
// __syscall(SYS_exit) would unlock the thread, list
// do it manually here
__tl_unlock();
free(self->map_base); free(self->map_base);
// Can't use `exit()` here, because it is too high level // Can't use `exit()` here, because it is too high level
return; return;
@ -212,10 +201,15 @@ static void __pthread_exit(void *result)
#ifdef __wasilibc_unmodified_upstream #ifdef __wasilibc_unmodified_upstream
for (;;) __syscall(SYS_exit, 0); for (;;) __syscall(SYS_exit, 0);
#else #else
// __syscall(SYS_exit) would unlock the thread, list
// do it manually here
__tl_unlock();
// Can't use `exit()` here, because it is too high level // Can't use `exit()` here, because it is too high level
/* On Linux, the thread is created with CLONE_CHILD_CLEARTID,
* and the lock (__thread_list_lock) will be unlocked by kernel when
* this thread terminates.
* See also set_tid_address(2)
*
* In WebAssembly, we leave it to wasi_thread_start instead.
*/
#endif #endif
} }

17
libc-top-half/musl/src/thread/wasm32/wasi_thread_start.s
View File

@ -28,4 +28,21 @@ wasi_thread_start:
local.get 1 # start_arg local.get 1 # start_arg
call __wasi_thread_start_C call __wasi_thread_start_C
# Unlock thread list. (as CLONE_CHILD_CLEARTID would do for Linux)
#
# Note: once we unlock the thread list, our "map_base" can be freed
# by a joining thread. It's safe as we are in ASM and no longer use
# our C stack or pthread_t. It's impossible to do this safely in C
# because there is no way to tell the C compiler not to use C stack.
i32.const __thread_list_lock
i32.const 0
i32.atomic.store 0
# As an optimization, we can check tl_lock_waiters here.
# But for now, simply wake up unconditionally as
# CLONE_CHILD_CLEARTID does.
i32.const __thread_list_lock
i32.const 1
memory.atomic.notify 0
drop
end_function end_function